1. Field of the Invention
The present invention relates to a pair of semi-spherical bevel gears and more particularly, to a pair of bevel gears which include a plurality of gear teeth and grooves radially disposed in the surface thereof from the summit thereof, respectively, so as to be in gearing relationship from each other at a variable angle for use in various types of machines, machine tools, control machines, testing machines, medical machines, robots, toys, and the like as a driving force transmitter.
2. Description of the Prior Art
Generally, a pair of conventional spur gears have a driving shaft and a driven shaft with a plurality of teeth, respectively, for gearing with each other in parallel so that only the ratio of rotation and the direction of the rotation are changeable. However, the gearing intersection angle of the two shafts cannot be change or varied.
Also, the conventional bevel gears can change in an engagement intersection angle of two shafts of the pair of conventional bevel gears. However, the engagement angle of such pair of bevel gears is determined according to an angle of the pitch circle. For example, when the angle of the pitch circle is 45.degree., the gearing intersection angle of two shafts becomes a right angle. When the angle of the pitch circle is 35.degree., the gearing intersection angle of two shafts becomes 70.degree.. Therefore, if once the gearing intersection angle is determined when the gears are designed and manufactured, the gearing intersection angle of the rotation cannot change any further. That is, it is not variable.
Also, conventional universal coupling devices wherein a pair of shafts intersect in a variable angle. However, the extent of variable intersection angle is within the limit of about 30.degree.. Furthermore, over the angular limit, the desired speed of rotation of the gears cannot be attained.
In such conventional gearing devices, the variable gearing intersection angle of the pair of shafts of the gearing devices during rotation is not taken into consideration at all. Only the strengthening of gear teeth for desirable gearing with each other has been considered. However, the displacement of the contact point of the pair of teeth of gears is not drawn any attention. Also, as a matter of fact, there are a number of requirements to moderate the strength of teeth and variable gearing intersection angle of the pair of gear shafts. In order to solve the requirements, the conventional multi-stage bevel gears are utilized. However, there are a number of disadvantages, for example, it is complicated in construction and expensive to manufacture.